Colorado Snowpack

THE MEASUREMENTS BEHIND THE PICTURE

Understand the snowpack.

Accepted observations · 2026-09-21. Measurements are checked twice daily. If an update fails validation, the site keeps the last verified readings.

Water held in snow.

Snow water equivalent (SWE) is the depth of water contained in snow, measured here in inches. It is not snow depth, new snowfall, or a forecast.

The dashboard displays the published NRCS station-based SWE series for Colorado statewide and all eight major basins used by the Colorado Snow Survey. These describe conditions at monitoring sites. They are not an estimate of every unit of water stored across the state or basin.

Statewide and eight river basins.

The menu groups the Colorado Snow Survey’s eight major basins by river system. Colorado Headwaters, Gunnison, Yampa–White–Little Snake, and San Miguel–Dolores–Animas–San Juan drain to the Colorado River. Laramie & North Platte and South Platte belong to the Platte system. Arkansas and Upper Rio Grande have their own groups.

These are NRCS’s published basin combinations; we do not split or recombine their measurements. Watersheds cross state lines, and the statewide product includes representative monitoring sites outside Colorado. Similarly named basins in other NRCS products may have different boundaries. The statewide reading comes directly from NRCS, not an average of the eight basin readings.

Official chart legends identify the stations included in each annual series. Those labels are not counts of stations reporting every day. Historical station populations vary, and the export does not provide daily coverage or weights. We therefore avoid claims of fixed coverage, total regional water volume, or sensor-level verification.

Sources: Colorado Snow Survey FAQ and NRCS products guide. The guide cautions that basin definitions can differ between products.

A fair seasonal comparison.

The reference is NRCS’s published 1991–2020 median series for the same month and day. We retain that series directly; we do not average basin percentages or substitute the period-of-record median. A median is a middle value, not a mean. About NRCS normals.

Where the reference is at least 0.1 inch, percent of median is the published SWE divided by the published reference, multiplied by 100. Below that threshold, small differences can produce unstable percentages, so we do not show a ratio. This threshold is our display rule, not an NRCS standard. A zero median does not imply no snow is present.

A water year begins October 1 and ends September 30. Water year 2026 is October 1, 2025 through September 30, 2026. Curves align by month and day. February 29 has no observation in a non-leap year; lines break there rather than shifting dates. Missing observations remain gaps. Measured zero remains zero.

The weekly note compares the snapshot date with exactly seven calendar days earlier. It describes the difference between published series values, not fresh snowfall. Changing coverage can affect small differences. Snow-water loss alone does not establish worsening conditions, runoff, or water-supply consequences.

Sources and verification.

We compared 137,982 annual/reference value positions in the statewide and eight basin NRCS JSON exports with their corresponding official chart traces. This checks product integration, not independent sensor accuracy. All measurements remain provisional and may be revised upstream. Accepted revisions are retained in a versioned history; each download identifies its accepted release.

The interactive chart offers water years 2024–2026, each with the preceding season. Full source history is in the downloads; the presence of a year does not guarantee complete coverage. Readings are rounded to hundredths for display. A positive value below 0.005 is shown as “<0.005,” not zero. Downloads preserve source precision.

Open data, without an account.

Download CSV · Download JSON · Metadata & provenance

Each observation includes a region identifier, calendar observation date, water year, SWE and reference in inches, percent of median when meaningful, reference period/statistic, and quality flags. Empty CSV fields and JSON nulls mean missing or unavailable, not zero. Quality flags identify provisional data, unverified daily coverage, missing values, and a near-zero reference. Observation dates differ from the UTC verification timestamp in metadata.

Exports retain schema 0.1.0 and use method accepted-v1. The compact dashboard snapshot has its own schema 1.0.0. Accepted revisions are retained in versioned history. Each download identifies its release.

import json
from urllib.request import urlopen
data = json.load(urlopen("http://127.0.0.1:8765/data/releases/2/series.json"))
rows = data["observations"]
state = [r for r in rows if r["region_id"] == "co-state"]

Attribute the underlying measurements to USDA NRCS and include the source product, observation date, and reference period when reusing them. These files are openly downloadable; no broader licensing claim is made here. For station-level research, use the upstream NRCS tools.

An independent information project.

ColoradoSnowpack.com is not a government service, a Colorado office, or a registered nonprofit. There are no ads, sponsors, paid memberships, or commercial promotions in this preview.

For a data or website issue, open an issue in the project repository. Issues are public: do not include subscriber addresses or private information. For newsletter account requests, reply privately to a newsletter email. No personal mailing address is published.

Maps, photography & type.

The contour background is traced directly from public-domain USGS National Map elevation contours near Longs Peak. The lines retain their mapped geometry at 200-foot elevation intervals. This fixed landscape detail is decorative; it does not show snow measurements or change with the selected basin.

The mountain photograph shows Longs Peak and Mount Meeker in Rocky Mountain National Park. Photo: NPS/D. Turk, via the National Park Service. It is a landscape photograph, not a report of current snow conditions. The site uses Manrope, a locally hosted typeface distributed under the SIL Open Font License.